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Shenoy" , Swapnil Sapkal , Ingo Molnar , Juri Lelli , Vincent Guittot , Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , linux-kernel@vger.kernel.org References: <20250904041516.3046-1-kprateek.nayak@amd.com> <20250904041516.3046-2-kprateek.nayak@amd.com> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: <20250904041516.3046-2-kprateek.nayak@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: WEBgESyanmAGKw8wuT_O1ApQt4MJxw5n X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTIwMDAyMCBTYWx0ZWRfX3dyFASGeRs7E GwlL4VcO90sKqMBcqcIbKgQWUjG/On3okQbMRgAG2wheyauw94UldH9c+rrFU03EFYi/m+bG3z5 Ctq8CaRZkuaxFi3CZqdGmE6BpAsrqVYyBxj+g6I9Jlp21kwOFFrbIG0WTLeFoVZlXliwZO1C96k SYbO+NdGpGvu/D/lAwlqI48N56Xd2ej2joMVID7wi8kVDpdA2z40jJwwW0IaHInqJLpaelkx52p waRyZxQ48OtVCLCSva1s880wSbYrqZVoas3prDxioNRDeUD7NxLFJQ1YeT06lu2xTfgB5SJY20K N8igt0qVobhQirB7cuXYnjlbDR8iBiQ7InCc9MOQBDZaB2U/h/xmqAdjdEk0ic1Dd3aEWQNvG76 KELOlM6b X-Authority-Analysis: v=2.4 cv=XYGJzJ55 c=1 sm=1 tr=0 ts=68d453e6 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=yJojWOMRYYMA:10 a=zd2uoN0lAAAA:8 a=VnNF1IyMAAAA:8 a=fHjAQ3KN5lqxBgJHjdkA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: T9IdPYAM-u8zPTZAlIVniIouUK16mcwx X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-09-24_06,2025-09-24_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 phishscore=0 clxscore=1015 adultscore=0 malwarescore=0 suspectscore=0 impostorscore=0 priorityscore=1501 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2509200020 On 9/4/25 9:44 AM, K Prateek Nayak wrote: > Simplify set_cpu_sd_state_{busy,idle}() using guard(rcu). > > Reviewed-by: Gautham R. Shenoy > Signed-off-by: K Prateek Nayak > --- > kernel/sched/fair.c | 20 ++++++++------------ > 1 file changed, 8 insertions(+), 12 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index df8dc389af8e..61b59fd75ced 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -12449,16 +12449,14 @@ static void set_cpu_sd_state_busy(int cpu) > { > struct sched_domain *sd; > > - rcu_read_lock(); > - sd = rcu_dereference(per_cpu(sd_llc, cpu)); > + guard(rcu)(); > > + sd = rcu_dereference(per_cpu(sd_llc, cpu)); > if (!sd || !sd->nohz_idle) > - goto unlock; > - sd->nohz_idle = 0; > + return; > > + sd->nohz_idle = 0; > atomic_inc(&sd->shared->nr_busy_cpus); > -unlock: > - rcu_read_unlock(); > } > > void nohz_balance_exit_idle(struct rq *rq) > @@ -12479,16 +12477,14 @@ static void set_cpu_sd_state_idle(int cpu) > { > struct sched_domain *sd; > > - rcu_read_lock(); > - sd = rcu_dereference(per_cpu(sd_llc, cpu)); > + guard(rcu)(); > > + sd = rcu_dereference(per_cpu(sd_llc, cpu)); > if (!sd || sd->nohz_idle) > - goto unlock; > - sd->nohz_idle = 1; > + return; > > + sd->nohz_idle = 1; > atomic_dec(&sd->shared->nr_busy_cpus); > -unlock: > - rcu_read_unlock(); > } > > /* This looks good. Reviewed-by: Shrikanth Hegde --- we have both sd_llc->shared and sd_llc_shared usage spread across the code, is it possible to remove sd_llc_shared and use sd_llc->shared instead? Likely sd_llc is cache hot and access to shared should be fast too. In turn this could free up some per cpu area. Any thoughts?